The present invention relates to a light receiving apparatus which is an image capturing apparatus which uses pulse light such as a pulsed laser as illumination light, mark detecting apparatus using the light receiving apparatus, exposing apparatus, maintenance method of exposing apparatus, manufacturing method of semiconductor device using exposing apparatus and semiconductor manufacturing plant.
In a semiconductor manufacturing apparatus (such as an exposing apparatus) which manufactures a memory with high density or a CPU with high specification, required exposure resolution is not more than 0.20 [xcexcm]. Thus, in order to transfer a finer pattern, a KrF laser (248 [nm]), an ArF laser (193 [nm]) and further an F2 laser (157 [nm]) are used as exposure light sources.
As part of a positioning method of the semiconductor manufacturing apparatus, there is a need for accurately measuring a positional relationship between a reticle which is an original plate or a reticle stage (original plate stage) on which the reticle is set and a wafer stage (substrate stage). The most advantageous measuring method thereof is TTR measurement for simultaneously measuring the reticle and stage. The TTR measurement is measurement carried out via a projection lens located between the reticle and stage. For an illumination light source used in the TTR measurement, exposure light is the most suitable. The reason is that aberration of the projection lens (such as chromatic aberration) is adjusted to the exposure light, which allows the reticle and stage to be simultaneously measured.
Presently, a main illumination apparatus which can emit light with high energy and short wavelength is an apparatus with an excimer laser or the like as a light source. Such a laser is a pulse light emitting laser (pulse light emitting apparatus).
An image capturing apparatus of a pulsed laser is disclosed in Japanese Patent Laid-Open Nos. 3-226187 and 5-190421, and the apparatuses disclosed in the specifications use the following four methods to generate images with reduced illumination non-uniformity.
(1) The illumination non-uniformity of the laser is restrained by oscillating means in an illumination apparatus.
(2) The laser is synchronized with a picture synchronizing signal input in the image capturing apparatus and is controlled to have the same number of pulses during light storage.
(3) In order to reduce the illumination non-uniformity, captured electrical signals are integrated.
(4) A cycle of the oscillating means is synchronized with the cycle of image capture.
FIG. 11 is a schematic view of a configuration of a light receiving apparatus according to a conventional example. Light of a pulse laser (Laser) 14 which is a pulse light emitting apparatus is leveled (uniformed) by oscillating means 7 such as a wedge, and after passing through mirrors 4, 5 and a half mirror 6, illuminates a mark of a wafer 3 on a substrate stage via a projection lens 2. After passing through the mirror 5 and half mirror 6 via the projection lens 2, the reflected light from the mark an image is imaged by a CCD camera (cam) 8 which is a storage-type position sensor. A synchronizing signal of the CCD camera 8 is generated by a synchronizing signal generator (Sync) 15. At the same time, the synchronizing signal is sent to the oscillating means 7 and laser (Laser) 14 to synchronize the CCD camera 8, oscillating means 7 and laser 14.
In FIG. 11, reference numeral 1 denotes a reticle; 9, driving means (motor); 10, an interferometer (inter); 11, a stage control apparatus (SF); and 12, an exposure control apparatus (com). Further, reference numeral 13 denotes a oscillating control apparatus (IS Cont); 16, an A/D converter; and 18, a control section for an image processing apparatus.
The CCD camera 8, which is of an NTSC system, stores light divided between even/odd timing, and as shown in FIG. 12, an oscillating cycle is adjusted to a cycle corresponding to an integral multiple of even/odd fields. FIG. 12 is an explanatory view of timing of the oscillating means, laser light emitting and image storing according to the conventional example.
In the conventional example, stored image data are added by an adder (sum) 17 shown in FIG. 11, and in FIG. 12, images of three or six frames are combined to generate images for measurement.
However, scan exposure has come to be carried out, which has caused the need for synchronizing the oscillating means with a scanning speed. That is, in the scan exposure, a resist on the wafer is irradiated with the light of the pulse laser as if a slit scanned over the wafer (substrate). In order to carry out exposure without illumination non-uniformity within a scanning area, exposure must be carried out in such a manner that a certain point on the wafer is irradiated with pulse light for one cycle or n cycles (n: natural number) of the oscillating means in a time period during which the point moves across the width of the slit. Thus, an increased scanning speed requires increased oscillation frequency of the oscillating means. The scanning speed is inversely proportional to energy for exposing the resist on the wafer, and an increased amount of exposure requires increased number of laser pulses (energy). Oscillation frequency of the laser is fixed (generally largest), so that a reduced scanning speed controls the oscillation frequency of the laser. In this way, for accommodating the scan exposure, the oscillating means must change an oscillation amount (oscillation frequency) in accordance with the scanning speed (exposure amount).
In case of storing the pulse light by the CCD camera of the NTSC system, the exposure time is limited to {fraction (1/60)} second. When the storage time is limited, oscillation by the oscillating means must be adjusted to an integral multiple of {fraction (1/60)} second in order not to produce illumination non-uniformity and not to cause even/odd difference at any time in imaging by an interlace system with even/odd time division specific to the NTSC system.
There is an optimum oscillation frequency requested in according with terms of the scanning speed, while the oscillation frequency must be adjusted separately in accordance with terms of the measurement, and each measurement requires control of the oscillating means. Generally, for changing in a short time an operation speed of an object moving at a high speed, control time for about a few second is required under the influence of inertia. In order to reduce the time to a few milliseconds, control means with high performance must be used. For this purpose, there is also a configuration which has oscillating means dedicated to measurement separately from the oscillating means for scanning.
However, the problem of the configuration is that the size of the illumination apparatus is increased and that double optical members for forming each oscillating means are required. Further, part of the light emitted from the light source must be directed to an optical system dedicated to measurement, which reduces illumination intensity for pattern exposure. Accordingly, the optimum configuration is such that part of an illumination system of a scan exposure system is utilized without making a dedicated optical system.
The TTR measurement is a measuring system which is used in calibration of a stage position and reticle position, calibration of a projection lens, or the like, and the measurement is carried out using wafer replacement time or the like. However, a recent exposing apparatus has the shortest wafer replacement time to increase throughput (wafer processing capacity per unit of time). In the measurement carried out in the wafer replacement, dead time of the apparatus is used until the oscillating means is stabilized.
The conventional system has a problem that the oscillating means must be controlled for image capture for measurement, which has influence on the throughput of the apparatus. When using in the image capturing apparatus a camera of the type that light storage divided between even/odd fields such as the NTSC system is carried out, difference in brightness (difference in illumination intensity) occurs between even/odd fields switched per 16.6 [msec] (={fraction (1/60)} sec). The following items are the causes of occurrence of the difference in the illumination intensity.
(1) The difference in the illumination intensity occurs under the influence of variation of laser energy in 16.6 [msec]. Especially, an amount of laser energy for a first pulse is relatively high and the amount is transitionally stabilized.
(2) The difference in the illumination intensity occurs by non-uniformity of the oscillation frequency of the oscillating means.
Harmful influence of the occurrence of the difference in the illumination intensity is poor accuracy of measurement of the captured image. For example, in measurement for quantifying a defocus amount by contrast of captured signals, accurate measurement cannot be achieved without constant amount of light. This is because the contrast value is varied by brightness.
Thus, reduction of the difference in the illumination intensity is required for improvement of the measurement accuracy. For this purpose, there are conventional methods including a method for increasing time (number of time) for integrating captured electrical signals and a method of discarding an image first captured by a camera. However, these methods have problems of requiring much time to capture images.
Another method is such that starting points of a capture start and the oscillating means are synchronized for each even/odd field. This method has disadvantage of increased time to capture images and also of complicated control of the oscillating means and capture.
Another problem of time-series capture of the even/odd fields is that all picture elements are not stored at the same time. A reticle stage and wafer stage are synchronously controlled, but when a first position of {fraction (1/60)} [sec] is different from a latter position of {fraction (1/60)} [sec], leveled light storage is not carried out but the images are changed in a stepping manner.
As a summary of the above descriptions, the prior art has the problems as described below.
(1) The oscillating means cannot be adjusted to the cycle of the image capture time in a short time. Adjustment over a long time has influence on the throughput.
(2) Capturing the image by the NTSC system causes non-uniformity of amounts of illumination light between even/odd fields, which has influence on the measurement accuracy.
(3) Capturing the image by the NTSC system has no synchronism between even/odd time-division images, so that occurrence of fine positional change prevents generation of integrated signals.
The present invention has been proposed to solve the conventional problems, and has as its object to provide a light receiving apparatus, mark detecting apparatus, exposing apparatus, manufacturing method of semiconductor device or the like, which can generate an image with high accuracy without changing oscillation frequency of oscillating means, permit increased accuracy in measurement, reduce measurement time and contribute to improvement of throughput.
In order to solve the above problems, the light receiving apparatus, mark detecting apparatus, exposing apparatus or the like according to the present invention have the following configurations.
A light receiving apparatus according to the present invention for uniforming pulse light emitted from a pulse light emitting apparatus by oscillating means and receiving the light by a storage-type position sensor may include means for obtaining pulse light emitting frequency of the pulse light emitting apparatus from a cycle of the oscillating means and predetermined number of pulses of the pulse light to start storage by the storage-type position sensor and emit the pulse light from the pulse light emitting apparatus by the obtained pulse light emitting frequency.
In the light receiving apparatus according to the present invention, the storage-type position sensor may preferably use a non-interlace type CCD camera which can control the storage time when the light is received by the storage-type position sensor.
In the light receiving apparatus according to the present invention, the storage-type position sensor may preferably use an interlace type CCD camera which can control even/odd (even field/odd field) storage time when the light is received by the storage-type position sensor.
In the light receiving apparatus according to the present invention, the storage time when the light is received by the storage-type position sensor may preferably start earlier than a pulse light emitting start and end later than a pulse light emitting end.
In the light receiving apparatus according to the present invention, the pulse light emitting apparatus may preferably use an excimer laser.
In the light receiving apparatus according to the present invention, the pulse light emitting apparatus may be preferably controlled by two steps of a dummy pulse light emitting step and a measurement pulse light emitting step, the storage by the storage-type position sensor being not carried out by the dummy pulse light emitting, but by the measurement pulse light emitting, the storage time of the storage-type position sensor and the pulse light emitting frequency being obtained from the cycle of the oscillating means and the predetermined number of pulses to start the storage by the storage-type position sensor and emit the pulse light from the pulse light emitting apparatus by the obtained pulse light emitting frequency.
In the light receiving apparatus according to the present invention, the storage start of the storage-type position sensor and the pulse light emitting from the pulse light emitting apparatus by the obtained pulse light emitting frequency may be preferably carried out simultaneously.
In the light receiving apparatus according to the present invention, the oscillating cycle of the oscillating means may be preferably adjusted to the pulse light emitting frequency by adjusting the oscillation frequency of the oscillating means to the storage time of the storage-type position sensor, there being no need for adjusting the oscillating means to an image capture cycle by the light receiving apparatus.
In the light receiving apparatus according to the present invention, there may be preferably no need for adjusting the oscillating means to measurement, permitting use of the oscillation frequency of the oscillating means in exposure.
In the light receiving apparatus according to the present invention, there may be preferably no need for synchronizing a staring point of the oscillating means with the storage start of the storage-type position sensor, controlling the storage time of the storage-type position sensor corresponding to an amount of the pulse light required for the measurement of a mark position or the like.
In the light receiving apparatus according to the present invention, the pulse light of a few pulses may be preferably first emitted to wait stabilization of energy of the pulse light and then start the storage by the storage-type position sensor for emitting light of required pulses.
A mark detecting apparatus according to the present invention may include a light receiving apparatus, a mark on a substrate being irradiated with the pulse light which is uniformed by the oscillating means and output by the pulse light emitting apparatus, reflected light from the mark being received by the storage-type position sensor to detect the mark.
The mark detecting apparatus according to the present invention may preferably measure an amount of light of the mark by the mark.
The mark detecting apparatus according to the present invention may preferably measure contrast of the mark by the mark.
The mark detecting apparatus according to the present invention may preferably measure a position of the mark by the mark.
An exposing apparatus according to the present invention for projecting a pattern on an original plate stage on a substrate of a substrate stage via a projection lens may detect one or both of a positioning mark on the original plate stage and a positioning mark on the substrate stage using the mark detecting apparatus.
An exposing apparatus according to the present invention for projecting a pattern on an original plate stage on a substrate of a substrate stage via a projection lens may detect one or both of a contrast measurement mark on the original plate stage and a contrast measurement mark on the substrate stage using the mark detecting apparatus.
A manufacturing method of a semiconductor device according to the present invention may include steps of:
locating a plurality of semiconductor manufacturing apparatuses including an exposing device in a plant; and
manufacturing the semiconductor device using the plurality of semiconductor manufacturing apparatuses.
The manufacturing method of the semiconductor device according to the present invention may preferably further include steps of:
connecting the plurality of semiconductor manufacturing apparatuses with a local area network;
connecting the local area network with an external network outside the semiconductor manufacturing plant;
obtaining information on the exposing apparatus from database on the external network using the local area network and the external network; and
controlling the exposing apparatus based on the obtained information.
The manufacturing method of the semiconductor device according to the present invention may preferably obtain maintenance information of the manufacturing apparatus through data communication by having access to database provided by a vendor or user of the exposing apparatus via the external network, or carry out production management through data communication with a semiconductor manufacturing plant different from the above described semiconductor manufacturing plant via the external network.
A semiconductor manufacturing plant according to the present invention may include:
a plurality of semiconductor manufacturing apparatuses including an exposing apparatus;
a local area network for connecting the plurality of semiconductor manufacturing apparatuses; and
a gateway for connecting the local area network with an external network outside the semiconductor manufacturing plant,
permitting data communication of information on at least one of the plurality of semiconductor manufacturing apparatuses.
A maintenance method of an exposing apparatus may include steps of:
preparing database which stores information on maintenance of the exposing apparatus on an external network outside a plant where the exposing apparatus is located;
connecting the exposing apparatus with a local area network in the plant; and
maintaining the exposing apparatus based on the information stored in the database using the external network and the local area network.
The exposing apparatus according to the present invention may preferably include a display, a network interface and a computer for executing software for network, permitting data communication of the maintenance information of the exposing apparatus via a computer network.
In the exposing apparatus according to the present invention, the software for network may preferably provide a user interface on the display which is connected to the external network outside the plant where the exposing apparatus is located and for having access to the maintenance database provided by the vendor or user of the exposing apparatus, permitting obtaining information from the database via the external network.
Image capture (such as a light receiving apparatus or mark detecting apparatus) synchronizes the image storage time with the oscillation frequency of the oscillating means. Then, the number of laser pulses for the image storage are always kept constant and the images with the same amount of light are always generated from the above number of laser pulses at any oscillation frequency (storage time). For that purpose, laser light emitting frequency and the storage time of the CCD camera are calculated from the oscillation frequency and the number of laser light emitting pulses, and the number of laser light emitting pulses and the laser light emitting frequency are set in the laser and the storage time is set in the CCD camera. The image is picked up by simultaneously starting laser light emitting and light storage by the CCD camera asynchronously with the oscillating means.
The most desirable image storage is storage by a non-interlace system for simultaneously storing all the picture elements rather than storing by even/odd time-series division. Timely changing differences in the illumination intensity are leveled and stored in all the picture elements on the stored image, so that no difference between even/odd fields occurs. The uniformity of the oscillating means not only has influence on all the picture elements on an average but also extremely increases brightness of the whole screen obtained for each capture and reproducibility of the uniformity. Even/odd storage also becomes effective by exposure time adjusted to the oscillation frequency rather than {fraction (1/60)} [sec] which is defined by a standard of the NTSC system. Further, there is no need for synchronizing the starting point of the oscillating means with the storing start, which permits providing a simplified system.
Adjusting the storage time to the oscillation frequency and adjusting the oscillating cycle to the laser light emitting (pulse) frequency so as to always store the pulse light of the same number permit stable image capture without change of brightness for each capture to improve measurement accuracy.
Further, by using a non-interlace camera, each of the pulsed laser light spreads through all the picture elements of the storage type image sensor, eliminating the difference in the illumination intensity. Further, the light spreading through all the picture elements is the light captured at the same time, so that no time error occurs with the measurement signal. The time error means shift of images which occurs due to difference between even/odd capture time.
Sensor storage time only may be controlled which corresponds to the laser oscillating time until reaching the amount of light (of the pulse light) required for measurement (of a mark position or the like). Thus, integration of the electrical signals is unnecessary. Moreover, there is no need for adjusting the oscillating means to the image capture cycle, which eliminates the need for increasing accuracy of the oscillating means.
Of course, there is no need for adjusting the oscillating means to the measurement, so that the oscillation frequency in exposure can be used to eliminate a stop condition of the apparatus due to the change of the frequency. Consequently, driving efficiency of the apparatus is increased and the throughput is improved compared to the conventional examples.
This system can contribute to improvement of both of the measurement accuracy and the throughput.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same name or similar parts throughout the figures thereof.